Fan casing with annular shell

ABSTRACT

An apparatus and method for a multiple layer fan casing surrounding a fan having a plurality of circumferentially spaced blades rotatable about a rotational axis and having a sub-portion defining a blade impact zone, the multiple layers comprising an inner fiber layer confronting the blades, an outer fiber layer overlying the inner carbon layer, a glass layer sandwiched between the inner and outer composite fiber layers.

BACKGROUND OF THE INVENTION

An aircraft engine, for example a turbine engine, air is drawn into thefront of the engine through an inlet, compressed by a compressor, andmixed with fuel in a combustor. The mixture is burned and passes througha turbine. The flow of combustion gas expands through the turbine whichin turn spins the shaft and provides power to the compressor. The hotexhaust gases are further expanded through nozzles at the back of theengine, generating powerful thrust, which drives the aircraft forward.

A fan casing can define the inlet and a fan formed by a plurality ofblades. Variable conditions exist in which an engine operates. Foreignobjects, such as birds, hailstones, ice, sand, and rain may be entrainedin the inlet of the engine where impact with portions of the engine canoccur, including impact with an interior of the fan casing. In somecases impact may cause a portion of the blade to become torn out whichis commonly known as fan blade out. The loose fan blade can impact theinterior of the fan casing as well.

The fan casing can be formed in part by composite materials formed towithstand impacts caused by foreign objects or fan blade outs. Dependingon the thickness and of the composite material in the fan casing, thecomposite material can add a significant amount of weight to the engine.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, the present disclosure relates to a turbine enginecomprising a fan having a plurality of circumferentially spaced bladesrotatable about a rotational axis, a multiple layer fan casingsurrounding the fan and having a sub-portion defining a blade impactzone, the multiple layers comprising, an inner composite fiber layerconfronting the blades, an outer composite fiber layer overlying theinner carbon layer, a woven glass layer sandwiched between the inner andouter composite fiber layers, wherein the inner composite fiber layer,outer composite fiber layer, and the woven glass layer overly the bladeimpact zone, and the outer composite fiber layer abuts the innercomposite fiber layer beyond the blade impact zone.

In another aspect the present disclosure relates to a multiple layer fancasing surrounding a fan having a plurality of circumferentially spacedblades rotatable about a rotational axis and having a sub-portiondefining a blade impact zone, the multiple layers comprising an innercomposite fiber layer confronting the blades, an outer composite fiberlayer overlying the inner carbon layer, a woven glass layer sandwichedbetween the inner and outer composite fiber layers, wherein the innercomposite fiber layer, outer composite fiber layer, and the woven glasslayer overly the blade impact zone, and the outer composite fiber layerabuts the inner composite fiber layer beyond the blade impact zone.

In another aspect the present disclosure relates to a method offabricating a multiple layer fan casing, the method comprisingfabricating an annular shell having a constant thickness, wrapping theannular shell with an annular casing wrap having at least one carbonlayer and at least one woven glass layer, confining the at least onewoven glass layer to a blade impact zone, and producing a point ofmaximum thickness of annular casing wrap within the blade impact zone.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional view of a turbine engine.

FIG. 2 is an enlarged view of a fan casing for the turbine engine ofFIG. 1.

FIG. 3A is a cross-sectional view of a middle portion of the fan casingtaken along line IIIA of FIG. 2.

FIG. 3B is a cross-sectional view of an aft portion of the fan casingtaken along line IIIB of FIG. 2.

FIG. 4 is a variation of the cross-sectional view of FIG. 3A accordingto another aspect of the disclosure described herein.

FIG. 5 is an enlarged view of the fan casing of FIG. 2 illustrating amethod of fabricating the fan casing according to an aspect of thedisclosure described herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure is related to a fan casing circumscribing a fanfor a turbine engine and having multiple layers and including asub-portion defining a blade impact zone. For purposes of illustration,the aspects of the disclosure discussed herein will be described withrespect to the fan casing for an aircraft turbine engine. It will beunderstood, however, that the disclosure as discussed herein is not solimited and may have general applicability within an engine, includingcompressors, as well as in non-aircraft applications, such as othermobile applications and non-mobile industrial, commercial, andresidential applications.

As used herein, the term “forward” or “upstream” refers to moving in adirection toward the engine inlet, or a component being relativelycloser to the engine inlet as compared to another component. The term“aft” or “downstream” used in conjunction with “forward” or “upstream”refers to a direction toward the rear or outlet of the engine relativeto the engine centerline. Additionally, as used herein, the terms“radial” or “radially” refer to a dimension extending between a centerlongitudinal axis of the engine and an outer engine circumference.Furthermore, as used herein, the term “set” or a “set” of elements canbe any number of elements, including only one.

All directional references (e.g., radial, upper, lower, upward,downward, left, right, lateral, front, back, top, bottom, above, below,vertical, horizontal, clockwise, counterclockwise) are only used foridentification purposes to aid the reader's understanding of thedisclosure, and do not create limitations, particularly as to theposition, orientation, or use thereof. Connection references (e.g.,attached, coupled, connected, and joined) are to be construed broadlyand can include intermediate members between a collection of elementsand relative movement between elements unless otherwise indicated. Assuch, connection references do not necessarily infer that two elementsare directly connected and in fixed relation to each other. Theexemplary drawings are for purposes of illustration only and thedimensions, positions, order, and relative sizes reflected in thedrawings attached hereto can vary.

A turbine engine 10 is illustrated in FIG. 1. The disclosure asdiscussed herein is not limited to use in a specific turbine engine, andthe engine shown in FIG. 1 is for illustrative purposes only. Theturbine engine 10 includes a fan assembly 11 and a core engine 13including a high-pressure compressor 14, a combustor 16, a high-pressureturbine 18, a low-pressure turbine 20, and a booster 22. The fanassembly 11 is surrounded by a multiple layer fan casing 23 and includesa fan 12 having an array of fan blades 24 extending radially outwardfrom a rotor disc 26. The fan assembly 11 can define an axial length (L)of an annular shell 25 comprising an inner composite fiber layer 27surrounding the fan 12. The engine 10 has an intake side 28 and anexhaust side 30. The fan assembly 11 and the low-pressure turbine 20 arecoupled by a first rotor shaft 31, and the high-pressure compressor 14and the high-pressure turbine 18 are coupled by a second rotor shaft 32.

During operation, air flows through the fan assembly 11, along a centralaxis 34, and compressed air is supplied to the high-pressure compressor14. The highly compressed air is delivered to the combustor 16. Airflow(not shown in FIG. 1) from the combustor 16 drives the fan assembly 11by way of the first rotor shaft 31.

FIG. 2 is an enlarged partial cross-sectional view of the multiple layerfan casing 23 from FIG. 1. The multiple layer fan casing 23 can at leastin part define the axial length (L) of the fan assembly 11. Morespecifically, the length (L) circumscribes a a sub-portion of the fancasing defining a blade impact zone 40 of the fan assembly 11. The bladeimpact zone 40 can be larger or smaller than illustrated and is definedas an axially extending region most likely to receive an impact from fanblade 24 in the event of a fan blade out (FBO). An FBO is when a portionof the fan blade 24 becomes torn out or dislodged from the fan assembly11, travels along a blade trajectory path 42, and impacts the multiplelayer fan casing 23. A blade trajectory path 42 is a path along which aportion of the fan blade 24 would most likely travel in the event of anFBO.

The inner composite fiber layer 27 of the multiple layer fan casing 23can be co-extensive with the fan casing such that it extends axiallythrough the full length (L). The inner composite fiber layer 27 canextend radially between an inner surface 44 and an outer surface 46maintaining a constant thickness (T) throughout. A non-limiting examplefor the inner composite layer 27 is use of a woven fiber. When the innercomposite fiber layer 27 is made out of a woven fiber, there can be aconstant number of weave layers across the whole length (L). Morespecifically all wraps extend across the entire length (L), and theweave is oriented such that the warp weave, fibers held stationary intension, direction is in the circumferential direction of the case andthe weft weave, fibers drawn through and inserted over and under thewarp weave, direction is in the axial direction of the case. In such acase, thickness changes in the composite fiber layer 27 can be achievedby adding or subtracting warp fibers. The thickness (T) affects thecapability, or strength and stiffness, of the inner composite fiberlayer 27. An inner composite fiber layer 27 having a greater thickness(T) decreases the axial capability of the annular shell 25 and increasesthe hoop capability while a lesser thickness (T) increases the axialcapability but decreases the hoop capability. A thickness (T) with awarp to weft fiber ratio of between 1:2 and 2:1 optimizes both the axialand hoop capabilities.

Multiple layers 52 form the multiple layer fan casing 23. The innercomposite fiber layer 27 is wrapped in additional layers to form anannular casing wrap 50 circumscribing the annular shell 25 along atleast a portion of the outer surface 46 of the annular shell 25 innercomposite fiber layer 27. The annular casing wrap 50 includes an outercomposite fiber layer 54 overlying the inner composite fiber layer 27with a woven glass layer 56 sandwiched therebetween. Each of theadditional layers 54, 56 can be wrapped about the annular shell 25 toform areas of varying thickness in the radial direction with an area ofmaximum thickness (T_(MAX)) located within the blade impact zone 40where the blade trajectory path 42 intersects the inner surface 44 ofthe inner composite fiber layer 27.

The outer composite fiber layer 54 abuts the inner composite fiber layer27 beyond the blade impact zone 40. The outer composite fiber layer 54can extend axially forward of the blade impact zone 40 to define aforward portion (F) of the annular casing wrap 50. The forward portion(F) extends forward from a contact point (Fp) where the woven glasslayer 56 terminates and the composite fiber layer 54 abuts the innercomposite fiber layer 27. It is further contemplated that the outercomposite fiber layer 54 can extend axially aft from the blade impactzone 40 to define an aft portion (A) of the annular casing wrap 50. Theaft portion (A) extends aft from a contact point (Ap) where the wovenglass layer 56 terminates and the composite fiber layer 54 abuts theinner composite fiber layer 27. It is contemplated that the forwardportion (F) and the aft portion (A) of the multiple layer fan casing 23include only the inner and outer composite fiber layers 27, 54. Theouter composite fiber layer 54 can co-extend with the fan casing 23 suchthat it is equal to the axial length (L) but greater than the axialextent of the blade impact zone 40. It is further contemplated that theouter composite fiber layer 54 is less than the axial length (L). Theouter composite fiber layer 54 can include multiple wraps of layers ofcarbon fiber material.

Turning to FIG. 3A, an enlarged view of the blade impact zone 40 isillustrated to more clearly distinguish the multiple layers 52 that formthe multiple layer fan casing 23. The woven glass layer 56 can be anytype of woven glass fiber, by way of non-limiting example an S2 classfiberglass. It is contemplated that any fiber having a higher punctureresistance than the fibers used in the inner composite fiber layer 27 orthe outer composite fiber layer 54, for example R-glass, can be used. Alist of such fibers can be found in the ASM Handbook, Vol. 21Composites. The outer composite fiber layer 54 can be, by way ofnon-limiting example, an intermediate modulus, IM, type 7 graphite. Theouter composite fiber layer 54 can be any carbon fiber suitable for acasing and is not meant to be limited. Both the woven glass layer 56 andthe outer composite fiber layer 54 can be formed with varying thicknesswithin the blade impact zone 40 such that the thickness is increasedtoward the maximum thickness (T_(MAX)) while tailoring the hoop andaxial capabilities of the multiple layer fan casing 23.

The inner composite fiber layer 27 can be formed by wrapping a wovenfiber preform material around the circumference of the case with thewoven layer extending across the entire axial length of the case. Thelayer can be infused with resin and cured using a resin transfer mold(RTM) process to achieve a composite material of a constant thickness(T). By way of non-limiting example, the inner composite fiber layer 27can be made from carbon fiber that has been woven to form a network offibers with most fibers in the plane of the weave, but having somefibers extending through the thickness to interlock the fiber layers ofthe weave. The through-thickness fibers could either extend fullythrough the thickness to achieve a 3D weave or partially through thethickness to achieve a 2.5 D weave as is described in Structure andMechanics of Textile Fibre Assemblies, P. Schwartz, Elsevier, 2008. Itis also contemplated that the inner composite fiber layer 27 is anytextile composite material having a woven, braided, non-crimp fabric forexample, but not limited to graphite fiber, glass fiber, ceramic fiber,or aramid polymer fiber.

Turning to FIG. 3B, an enlarged view of the aft portion (A) isillustrated to more clearly distinguish the outer composite fiber layer54 annular shell 25. It should be understood that this enlarged view canalso represent the forward portion (F). The inner composite fiber layer27 has the same thickness (T) as illustrated in FIG. 3A while theannular casing wrap 50 only includes the outer composite fiber layer 54within the forward portion (F) and aft portion (A).

Turning to FIG. 4, it is further contemplated that another layer 60,which can be by way of non-limiting example a woven layer, overlies theouter composite fiber layer 54 to form three distinct layers ofmaterials within the annular casing wrap 50. The other layer 60 can beformed from the same material as the woven glass layer 56, by way ofnon-limiting example S2 Fiberglass. It is contemplated that the otherlayer 60 is a different material than the woven glass layer 56, by wayof non-limiting example a material with higher elongation capabilitythan carbon such as S-glass, E-glass, Kevlar, or Dyneema. It is furthercontemplated that the other layer 60 extends along the entire axiallength (L1) of the annular ramp such that it is the same length as outercomposite fiber layer 54. It is also contemplated that other layer 60extends into one of the forward portion (F) or aft portion (A) such thatthe annular casing wrap 50 includes two layers within the forwardportion (F) or aft portion (A), where the two layers are the other layer60 and the inner composite fiber layer 54.

A method 200 of fabricating the multiple layer fan casing 23 isdescribed below with reference to FIG. 5. The method 200 includes at 202fabricating the annular shell 25 out of an inner composite fiber layer27 with a constant thickness (T). At 204, the annular shell 25 iswrapped with the additional layers to form the annular casing wrap 50including at least one carbon layer, by way of non-limiting example theouter composite fiber layer 54 and at least one woven glass layer, byway of non-limiting example, the woven glass layer 56. It should beunderstood that forming the multiple layers 52 can include forminganother layer 60, as described herein, where the other layer 60 overlaysthe outer composite fiber layer 54. At 206 the at least one woven glasslayer 56 is confined to just the blade impact zone 40. The methodfurther includes at 208 producing a maximum thickness (T_(MAX)) ofannular casing wrap 50 at a point (P) along the annular shell 25 withinthe blade impact zone 40. The point (P) is defined as the point wherethe blade trajectory path 42 intersects the multiple layer fan casing23.

The method 200 can further include at 210 abutting the at least onecarbon layer with the annular shell 25, by way of non-limiting exampleabutting the inner composite fiber layer 27 with the outer compositefiber layer 54 outside the blade impact zone 40. Finally, the method canalso include at 212 tapering at least one of the carbon layer 54 orglass layer 56 from the point (P) to where the outer composite fiberlayer 54 abuts the inner composite fiber layer 27. By way ofnon-limiting example, as illustrated, the woven glass layer 56 of glassis tapered in both the forward and aft direction such that the annularcasing wrap 50 forms a substantially trapezoidal shape within the bladeimpact zone 40.

When compared to a layered casing without additional woven glasslayer(s), the annular casing wrap 50 can minimize or eliminate back-sidefiber failure. In other words, through holes from blade impacts do notoccur in the middle portion of the annular casing wrap 50. Duringtesting, impacts to areas with and without the additional layers arecompared to form a baseline damage amount on the inner surface 44. Thisbaseline damage amount is the amount of damage sustained in both areasuntil the damage beings to increase in one of the areas when compared toeach other. Even with kinetic energy increases up to 20% above thebaseline damage amount, zero through holes were formed in the bladeimpact zone 40 of the annular casing wrap 50. Tailoring the annularcasing wrap 50 to cover these areas minimizes weight for the multiplelayer fan casing 23 and maximizes performance of the multiple layer fancasing 23 during an FBO.

Benefits associated with the fan casing as described herein include alightweight annular shell conducive to automated manufacturing due tothe constant thickness and homogeneous material. Including the pluralityof layers within the annular casing wrap facilitates the ability totailor the thickness of the annular casing wrap to locations where morethickness is needed. The wrapping aspect also enables rapid modificationin terms of the placement of the layers. Wrapping the annular shellminimizes any excess weight and localizes necessary thickness in theannular casing wrap.

To the extent not already described, the different features andstructures of the various aspects can be used in combination with eachother as desired. That one feature cannot be illustrated in all of theaspects is not meant to be construed that it cannot be, but is done forbrevity of description. Thus, the various features of the differentaspects can be mixed and matched as desired to form new examples,whether or not the new examples are expressly described. Combinations orpermutations of features described herein are covered by thisdisclosure. Many other possible embodiments and configurations inaddition to that shown in the above figures are contemplated by thepresent disclosure.

This written description uses examples to disclose aspects of theinvention, including the best mode, and also to enable any personskilled in the art to practice aspects of the invention, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the invention is defined by the claims,and can include other examples that occur to those skilled in the art.Such other examples are intended to be within the scope of the claims ifthey have structural elements that do not differ from the literallanguage of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

What is claimed is:
 1. A turbine engine comprising: a fan having aplurality of circumferentially spaced blades rotatable about arotational axis; a multiple layer fan casing surrounding the fan todefine a circumferential direction and extending axially to define a fancasing axial length and having a sub-portion axially extending regiondefining a blade impact zone, the multiple layers comprising: an innercomposite fiber layer co-extensive with the fan casing extending anaxial length equal to the fan casing axial length and confronting theblades, an outer composite fiber layer overlying the inner compositefiber layer; and a woven glass layer sandwiched between the inner andouter composite fiber layers made from fibers having a higher punctureresistance than the fibers used in the inner composite fiber layer orthe outer composite fiber layer; wherein the inner composite fiberlayer, outer composite fiber layer, and the woven glass layer overly theblade impact zone, and the outer composite fiber layer abuts the innercomposite fiber layer beyond the blade impact zone.
 2. The turbineengine of claim 1 wherein both the inner and outer composite fiberlayers are co-extensive with the fan casing extending an axial lengthequal to the fan casing axial length.
 3. The turbine engine of claim 1wherein the outer composite fiber layer extends an axial length lessthan the inner composite fiber layer.
 4. The turbine engine of claim 1wherein the woven glass layer is coextensive with the blade impact zone.5. The turbine engine of claim 1 wherein the woven glass layer defines athickness in the radial direction that varies in the axial direction. 6.The turbine engine of claim 5 wherein the woven glass layer tapers froma point where a blade trajectory path intersects the fan casing untilterminating in a point where the outer composite fiber layer abuts theinner composite fiber layer.
 7. The turbine engine of claim 6 wherein atleast one of the inner or outer composite fiber layers has a constantthickness.
 8. The turbine engine of claim 7 wherein the inner compositefiber layer has a constant thickness.
 9. The turbine engine of claim 1further comprising another layer overlying the outer composite fiberlayer.
 10. The turbine engine of claim 1 wherein at least one of theinner or outer composite fiber layers is a carbon fiber.
 11. The turbineengine of claim 10 wherein the carbon fiber is graphite.
 12. The turbineengine of claim 1 wherein the inner composite fiber layer is a textilecomposite material.
 13. The turbine engine of claim 1 where the innercomposite layer is formed from a woven fiber with a weave oriented suchthat the warp weave direction is in the circumferential direction of thefan casing and the weft weave direction is in the axial direction of thefan casing.
 14. A multiple layer fan casing surrounding a fan having aplurality of circumferentially spaced blades rotatable about arotational axis and having a sub-portion defining a blade impact zone,the multiple layers comprising: an inner composite fiber layerconfronting the blades and formed from a woven fiber with a weaveoriented such that the warp weave direction is in a circumferentialdirection of the fan casing and the weft weave direction is in an axialdirection of the fan casing, an outer composite fiber layer overlyingthe inner composite fiber layer, a woven glass layer sandwiched betweenthe inner and outer composite fiber layers, wherein the inner compositefiber layer, outer composite fiber layer, and the woven glass layeroverly the blade impact zone, and the outer composite fiber layer abutsthe inner composite fiber layer beyond the blade impact zone.
 15. Themultiple layer fan casing of claim 14 wherein at least one of the innerand outer composite fiber layers is co-extensive with the fan casing.16. The multiple layer fan casing of claim 15 wherein the outercomposite fiber layer extends an axial length less than the innercomposite fiber layer, and the inner composite fiber layer isco-extensive with the fan casing.
 17. The multiple layer fan casing ofclaim 16 wherein the inner composite fiber layer has a constantthickness.
 18. The multiple layer fan casing of claim 16 furthercomprising another layer overlying the outer composite fiber layer. 19.The multiple layer fan casing of claim 14 wherein the woven glass layeris coextensive with the blade impact zone.
 20. The multiple layer fancasing of claim 19 wherein the woven glass layer varies in thickness inthe radial direction.
 21. The multiple layer fan casing of claim 20wherein the woven glass layer tapers from a point where a bladetrajectory path intersects the fan casing until terminating in a pointwhere the outer composite fiber layer abuts the inner composite fiberlayer.
 22. The multiple layer fan casing of claim 14 wherein at leastone of the inner or outer composite fiber layers is a carbon fiber. 23.A method of fabricating a multiple layer fan casing, the methodcomprising: fabricating an annular shell having a constant thicknessfrom a woven fiber with a weave oriented such that the warp weavedirection is in the circumferential direction of the fan casing and theweft weave direction is in the axial direction of the fan casing;wrapping the annular shell with an annular casing wrap having at leastone carbon layer and at least one woven glass layer; confining the atleast one woven glass layer to a blade impact zone; and producing apoint of maximum thickness of annular casing wrap within the bladeimpact zone.
 24. The method of claim 23 wherein the wrapping the annularshell further includes abutting the at least one carbon layer with theannular shell outside the blade impact zone.
 25. The method of claim 24further including tapering at least one of the carbon layer or glasslayer from the point of maximum thickness to where the at least onecarbon layer abuts the annular shell.